UR242 audio cuts out on iMac

I recently bought a UR242 interface, and have been very happy with it. But now it is randomly cutting out audio on playback. This occurs in Logic Pro X, but also on iTunes.

I first thought it might be defective, but found some threads where people were having that problem in Windows. I’m running Logic Pro X on an iMac with OSX El Capitan, version 10.11.2, and wondered if others have had the same problem.

Would love some advice on what to do in order to resolve this issue, thanks.